Means for and method of corrugating metal strip



A. G. GETZ July 27, 1954 MEANS FOR AND METHOD OF CQRRUGATING METAL STRIP Filed March 23, 1951 7 Sheets-Sheet l INVENTOR. Zrnszeczd 6% G66? A. G. GETZ July 27, 1954 MEANS FOR AND MEfIHOD OF- CORRUGATING METAL STRIP Filed March 23. 1951 7 Sheets-Sheet 2 July 27, 1954 @511 2,684,707

MEANS FOR AND METHOD CORRUGATING 'METAL'STRIP Filed March 23, 1951 7 Sheets-Sheet 3 July 27, 1954 A. G. GETZ 2,684,707

MEANS FOR AND METHOD OF CORRUGATING METAL STRIP Filed March 25, 1951 7 Sheets-Sheet 4 I] Z5 33 I '11" I I X" H Hh Z6 .ml H l. 2 I: '1 Z5 Il {1/ MW "W 32 I N V EN TOR.

July 27, 1954 A.'G. GETZ 2,684,707 MEANS FOR AND METHOD OF CORRUGATING METAL STRIP Filed March 23, 1951 I I 7 Sheefcs-S heet 5 INVENTOR.

msi ead Q Gezf'z BY y y 1954 A. G. GETZ 2,684,707

MEANS FOR AND METHOD OF CORRUGATING METAL STRIP Filed March 25, 1951 7 Sheets-Sheet 6 INVENTOR.

A. G. GETZ 2,684,707

July 2 7, 1954 MEANS FOR AND METHOD OF CORRUGATINGMETAL STRIP '7 sl leets-sheet 7 Filed March 23, 1951 Ank\ h Z RQ mmvroa G. Gei'z Patented July 27, 1954 MEANS FOR/AND METHOD-OF CORRU- GATIN G METAL STRIP Arnstead G. Getz, Lakewood, Ohio, assignor to The: Bishop & Babcock Manufacturing-Colla pany, Cleveland, Ohio,- a corporation eta-Ohio Application March 23, 1951, SerialNo. 217,228

9 Claims.

This invention relates to cores for heat exchange units such as automobile radiators and heaters, and has to" do with'means for and a method! of corrugating metal strip to be used in such .oores for forming the air passages thereof.

It'is known, in constructing cores of; the character referredto, to provide metal strips formed: with corrugations or projections, usually of" straight line contour, which strips when assembled" in the core define between them air passages" having interior projections for in1'-- parting'turbulence to the air and assuring contact thereof with the' metal of the core. The

strips are formed of' quite thin metal, such asele'ctrolytic copper having a thickness of approximately .O035 and, under'present practice, usually are formed to desired shape by subjectingthem to pressure between opposed form-' ing surfaces conforming to the desired contour ofthe ultimate form of the strip. During such v formingoperation'the thin metal strip is sub-' jected to considerable pressure between'rela-tively moving opposed forming surfaces and is frequentlytorn or ruptured in the forming operation. That results in objectionable waste of metalan'd also necessitates care in designing-the final form of the strip so-as to reduce, as far as possible, wastage. As noted; the final form-of the strip usuallyiis' so designed that the corrugations or projections thereof are defined-' by 9 straight lines, with a view to reducing tearing of thestrip'andresultant wastage to a minimum. It has been attempted-toproduce strips having projections or' corrugations defined by curvedi'lines but, in general, the resultant wastage, due to rupture anditearing of the metal; when using the present methods above referred to, has been'so great as to beprohibitive;

My invention is directed to the production of corrugatedmetal strip of desiredfinal formwvithout incurring'the wastage ofmetal' which occurs under the present practice above referred to. is directed particularly to the production of corrugated metal strip providedwith' corrugations which are undulatory lengthwise, without subjecting the strip to forming pressurebetween opposed forming and pressure applying surfaces of the metal strip so as to avoid subjectingiit to pressure between opposed forming surfaces. When the strip v has been preformed in :theman ner stated, it is subjected-to afinalforming opera/tionsimilar to the preforming operation, the height and spacing of the forming elements or 1'i-bS"l.lSd in the preforming operation being so related to the height andspacing of the form.- ing elements or ribs used in the final forming operation as to render available for the latter operation adequate metal'such that anyxobjectiona'ble stretching or thinning of the metal in thefi'nal forming operation is avoided. In both the preforming operationand the final forming operation the strip is at no time subjected to forming pressure between opposed forming surfaces thereby eliminating risk of rupture or tearing of the metal strip from that cause. Thepreforming operation is accomplished by opposed members, conveniently corrugating rolls, provided. with spaced apart forming elements or: ribs of such height and spacing that, in the rotation of the rolls, the ribs or each thereof enter midway between the ribs of the other roll with clearance therebetween materially greater than the thickness of the metalrstrip. Preferably, the ribs areof undulatory formation lengthwise. During rotation of the rolls, the metal strip is drawn between them and is pulled about the ribs in contact with the radially outer edges only thereof so as tobe' formed into. corrugations also. of undulatory formation lengthwise, the metal strip beingat no time subjected to. forming pressure between opposed forming surfaces. Ifhe preformed-metalstr'ip passes from the'preforming members or rolls tothefinal forming. members, preferably also two opposed. .corrugating rolls similar to the preforming rolls but having the formingelementsor ribs thereof of slightly less height-and -greaterspacing than the ribs .of the preformi-ng rolls,- to avoid any. objectionable such. as would be apt to cause rupture'ortear K distance materiallt greater than thethickness I form the strip to stretching ofthe metal in the final'forming operation, as-aboveexplained. In certain cases it is desirable to provide the corrugations of thefinally formed strip with lateral bosses or projections; to increase the airturbulence and :metal contact in thecore-embodying such strips; In such cases the final-formingoperation preferably is-performed'in opposed fiat dies having formingelements-"or-ribssimilar to those of the -corrugating rolls just referred to but provided with lateral' projections or bosses for forming bosses or projections 'inthe corrugations of the finally formed strip. In the'method of my invention, as willbe'iunderstood from what has been said,

the metal strip is pulled about the forming elements or ribs of the corrugating members so as to conform to the shape thereof, but is at no time subjected to forming pressure between opposed forming surfaces, thereby eliminating risk of tearing or rupture of the strip from that cause, as has been explained above. Further objects and advantages of my invention will appear from the detailed description.

In the drawings:

Figure 1 is a side view, partly broken away, of a metal strip corrugating machine embodying my invention;

Figure 2 is a side view of the machine of Figure 1, as seen from the side opposite to that shown in Figure 1, with certain parts shown in the latter figure omitted;

Figure 3 is a sectional view, on an enlarged scale, taken substantially on line 3-3 of Figure 1;

Figure 4 is a side view, on an enlarged scale, of one of the forming elements or ribs of the preforming rolls shown in Figure 3;

Figure 5 is a plan view of the rib shown in Figure l;

Figure 6 is a side view, on an enlarged scale, of one of the ribs of the final forming rolls;

Figure 7 is a plan view of the rib of Figure 6;

Figure 8 is a fragmentary plan view, on an enlarged scale, of the rib of Figure '7;

Figure 9 is a fragmentary end view, on an enlarged scale and partly broken away, of one of the preforming rolls and its associated shaft;

Figure 10 is a fragmentary semi-diagrammatic view, on an enlarged scale, showing in end view the two preforming rolls and metal strip passing between them;

Figure 11 is a view similar to Figure 10 but showing the final forming rolls;

Figure 12 is a fragmentary face view of the preformed corrugated metal strip produced by the preforming corrugating rolls;

Figure 13 is a fragmentary face view of the corrugated metal strip produced by the final forming corrugating rolls;

Figure 14 is a side view of a modified form of metal strip corrugating machine embodying my invention, used for effecting the preforming operation on the metal strip;

Figure 15 is a fragmentary side view of two opposed dies suitable for performing the final forming operation on the preformed strip produced by the machine of Figure 14, the dies being shown partly broken away and in section;

Figure 16 is a fragmentary plan View of the lower die of Figure 15;

Figure 17 is a fragmentary lengthwise sectional view, on an enlarged scale, of the dies of Figure 15 closed on the metal strip therebetween;

Figure 18 is a fragmentary face view, on an enlarged scale, of the finallyformed corrugatedmetal strip produced by the dies of Figure 15; and

Figure 19 is a sectional view taken substantially on line Iii-l9 of Figure 18.

The machine shown in Figure 1 comprises a suitable base or table 20 to which are secured two pairs of spaced uprights 2i and 22. Upper and lower preforming rolls 23 are rotatably mounted in the uprights 2 l, aligned lengthwise of table 29 with upper and lower final forming rolls 25. As is shown more clearly in Figure 9 each of the preforming rolls 23 comprises a cylindrical body having an axial bore for reception of a shaft 25 on which body 25 is suitably secured, conveniently by means of keys 2?. Body 25 is provided with a plurality of lengthwise slots uniformly spaced circumferentially thereof and opening through the ends and the outer circumferential face of body 25. The slots in body 25 receive forming elements or ribs 28, shown more clearly in Figures 3, l and 5, which are of undulatory formation lengthwise and are straight and of substantially uniform thickness radially of body 25 of roll 23. The ribs 28 preferably are formed of cold rolled steel and are milled off for the major por tion of their height to provide spaced fingers 29 extending downward from the rib 23, between end fingers of materially greater extent length-- wise of rib 23 than the fingers Z9 and straight lengthwise of rib 28, the outer or upper portions of the fingers at providing straight terminal ex tensions of the rib 28. Each of the fingers 3c is provided, in its outer edge, with a rectangular notch 3i which registers with a rectangular annular groove 32 in the end of the roll body 25. A locking ring 33 fits snugly in groove 32 and in the notches 3! of fingers 3t, thus locking the ribs 28 tightly in position in the roll body 25. The ring 33 is retained in position by an annular plate 35 seating thereon and on the end of body 25 and secured to the latter in a suitable manner, conveniently by means of screws 36. As will be understood, there is a locking ring 33 and plate 35 at each end of body 225 of roll 23. The end portion of shaft 28 of each of the rolls 23 is of reduced diameter and is rotatably mounted in suitable bearings 38, mounted in the uprights 2 i as is shown more clearly in Figure 3.

The ribs 28 are all of the same effective height and project radially outward beyond body 25 of the respective rolls 23 a distance appreciably less than the space between the bodies 25 of rolls 23, and are rounded at their outer edges, as shown more clearly in Figure 10. The rolls 23 are relatively off-set angularly so that in the rotation thereof the ribs 23 of each roll :3 enter midway between the ribs 28 of the other roll, with considerable clearance therebetween. Meshing spur gears 38*, secured on the corresponding ends of shafts 26 of rolls 23, assure that both thereof will be rotated at the same speed, the gear ratio being appropriate to that end, while maintaining the proper angular relation between the rolls and also assuring that they will be rotated in opposite relation. Accordingly, when either of the preforming rolls 23 is rotated, the other roll will also be rotated at the same speed and in opposite relation, and the ribs 28 of the rolls will enter between each other as above explained, these ribs being of such height that the ribs of each roll at all times clear the ribs of the other roll during rotation of the rolls, as will be understood from what has been said.

A bevel gear M3 is secured on shaft 26 of the lower roll 23, at the opposite end thereof from the spur gear 33*, and meshes with a bevel gear at secured on shaft d2 of a speed reducing unit :53 of suitable known type, mounted on table 26 to one side of one of the uprights 2 l. A second shaft 44 of unit it is driven, through a suitable coupling it of known type, by shaft it of an electric motor 4'? mounted on table 29., It will be clear, from what has been said, that when the motor ll is in operation the two preforming rolls 23 are driven at the same speed and in opposite relation, it being understood that the unit it is selected to drive the rolls '23 at appropriate speed.

The final forming rolls 2d are similar to the preforming rolls 23 and a brief description thereof will suffice. Each of the rolls 2% comprises a answer cylindrical body u re ed onie shaft fl rotarelatively wide endfingers 'fl -straight lengthwise of rib fl i the-upper portions of which pro-- videstraight" continuations or terminalelements of" the rib 42?- Each of the fingers 44 is 'provi'ded'-with a rectangular notch lt in its outer edge; these-notches 46 "reoeiVing-1ockingrings fitting therein and in= annular recessesinthe ends of body-40 held in position-by retaining platessecured tdthe emlsof body 40*; as in the preformin rolls 232 The upper or radially outeredge of each rib 42 is-flat; as shown" more clearly in" Figures '6 and 11, and each undulation of rib 42 is-providedat theouter-side thereof with-a boss or projection 48 of approximately semi-elliptical shape plan having" an inner-face 49 straightlengthwise of rib- 42 and'an outer-face conformingto the curvature of the-corresponding undulation-of rib 42-? Theefiective height ofribs 42 that isthe extent to whichthey project beyond the body of roll=40 to the flat upper edges thereof; butnot including the bosses-48, is less than the effective height of the ribs 28-01 thepreforming rolls 2-3" by an" amount equal to the heightof bosses 48, the effectiveheight of ribs 42 at the bosses 48-beingrequal to' the effective heightof' the ribs 28of preforming rolls 23;" as willbe clear from Figures4; 6, "and-11. Also,- the ribs- 42 of the final forming rolls 24 are spaced somewhat further apart than'the ribs 28 of the preforming rolls 23; as shown in Figures 10 and'll; for a purpose which will appear later:

The effective height orradial extent of the ribs t2 beyondbodies'M) of thefinal forming: rolls 24 is appreciably less 'than' the distance between bodies' ifl as shown in Figure 1-1. Thefinal'forming rolls 24 are angularly oiT-set onehalf the distance between adjacent ribs 42' thereofso that the ribs-of each roll, during rotation thereof, entermidway between the ribs' off the other roll with clearance therebetween materially greater than the thickness of the metal strip operated upon. As willbe understood from what has been said, the spacing and radial eX tent of" the ribs 42? is such that there is at all times, during'rotation of the rolls, ample clearance'between the ribs thereof to guard against subjecting the metal strip to pressure between: th'erribs; which is also true of the preforming; rolls, as above noted.

Meshingspur gears 50 secured-on the ends of shafts- 41; adjacent one of' the uprights 22, assure-that the rolls -24-will be'driven at the same speed and in opposite direction and that't'heangular relation therebetween will 7 be maintained; A sprocket-wheel 52-issecured on'shaft 26of theupperpreformingroll 23-; at-the opposite end thereof fromspur gear 38.- This sprocket wheel- 52 has driving connection, through a sprocket chain 53, toa similar'sprocket wheel'54 seoured-on shaft 4W of the-upper final forming roll at the endthereof opposite to spur gear 505' Itwill' beseen that when the preforming rolls are-driven, thefinal forming rollsfl are also driven; the rolls of:each.=.pain-beingidrivenat.

the same speed and in opposite-relation and'the: rolls ofiboth :pairszbeingzdrivent at' the .same speed and in thesame relation, that is, the. upperrollsw are driven-sat the same speed andin the, same. direction and the lower rolls; are driven; at: the same i'speediasrthe upper rollspandiinz the: opposite direction relative thereto The two pairs: of rolls; are aligned-.1 forsrecep tion between themiottheimetalstrip beinglopera'ted upon. As tlie: finally.- formed metal strip passesabeyond the final forming. rolls 24; ,it is cut to'l'ength by suitable cut-off means; Conveniently, two opposedcut-off blades 51: and. are.

slidablymountedinslotteduprights, one of which shown at 59 secured to table 20 in. spaced. relation-transversely thereof, The upper blade 514 is pivoted at eachend" thereof, at 60, to; a.

linle- 61 pivoted at its lower end, at 62., to the inner end of a lever-"B3 pivoted at-itsmid -point at'fi li on a bracket-65" secured to upright 59: and

extending rearwardly therefrom; The: forward.

end of lever GSiscOnnected, bya pin and-slot connection, to thelower blade 58; A tension spring 61- is anchoredat its lower'end to pivot 6% and at itsupper end to upright 59. This springBTtendsto straighten-the toggle comprisin the link 6| and the inner arm of lever 63, thus-urging the upper blade 51 upward, such upwardmovementof' blade 51 being limited bystop screws; one-of whiohis shown at S3, threadedthrough-a cross piece?!) connecting the upper ends" 'ofthe uprights 59;

The lever 63 is provided with a downwardly for-moving the-latter forward In the forward movementofrodltthe blades 57' and 58'aremoved" toward" each other andare eifective for severingthe metal strip passing therebetween, aswillbe clear. When the nose I8 passes out ofcontact with the lever-1%; theblades 57- and" 58" are returned to theirnormal positions shown in 'Fi'gure 1, by" the tension springs-67; and'the'rod 13' is moved rearward'into position'with the roller' 19 disposed for contact" by nose It; as'shown; It will'be seen that'the cut-off means isoperated in timedirelationtothe rotation of the rolls, the" timing beingsuch that-the finally formedstrippassin from'the rolls 24 is-cut into lengths of predetermined and desired extent.

Two bracket arms l8?',,slotted from their'upper ends, are secured to and extend upwardly and rearwardly from the uprights 25;

The arms l8 receive the endsof'a shaft l9; rotatably mounted therein and carrying aroll 8b of metal strip or ribbon 8| of appropriate width and thickness,

=thismetal; strip commonly being, quite thin, as;

' while not imposing suliicient drag on therollto.

cause objeotionab'le tensioning of the metal strip 8 1 thus assuring that the metaLstripds drawn smoothly from the roll as required in the operation of the machine.

As the metal strip BI passes between the preforming rolls 23 it is pulled about the ribs 28 thereof, as shown diagrammatically in Figure 10, and is corrugated transversely, the crests of the corrugations thus produced being rounded as shown. It will be noted that there is considerable clearance between the ribs and the metal strip pulled thereabout, and that at no time is the metal strip subjected to forming pressure between opposed relatively moving pressure applying surfaces. The metal strip 8i conforms to the lengthwise formation of the ribs 28 as it is pulled thereabout, and the preformed strip leaving the rolls 23 is provided with corrugations 82 of substantially V cross section and of undulatory formation transversely of the strip for substantially the full width thereof, except for terminal elements 83 which are straight transversely of the strip; as shown in Figure 12. By avoiding subjecting the strip to pressure between opposed forming surfaces, I eliminate risk of tearing and rupture of the strip from that cause, thereby eliminating wastage while also rendering it possible to corrugate the metal strip at comparatively high speed with resultant increase in production.

The preformed strip BIa passes from the preforming rolls 23 over a supporting shelf 85 mounted between the pairs of uprights 2i and 22 and extending therebetween. From the final forming rolls 2d the strip passes over a second shelf 8% supported between the uprights 22 and thence over two spaced shelves 8? carried by the uprights 59. In the passage of the preformed strip iiia between the final forming rolls 2d, the crests of the corrugations 82 thereof are flattened, the corrugations are slightly spread or opened up, and the bosses 48 move corresponding areas of the corrugations outward beyond the flattened crests. The resultant finally corrugated strip dip is provided with transversely ex tending corrugations 99 of undulatory formation for the major portion of their length and having straight terminal elements 9| transversely of the strip, the corrugations 96 being provided at the outer side of each undulation thereof with a boss or projection 92 of relatively slight height having an inner surface straight transversely of the strip. By having the forming elements or ribs 42* of the rolls 2d of less effective height than the ribs 28 of the preforming rolls 29, I render available adequate metal for forming the corrugations to final shape between the rolls 24 in the manner stated without subjecting the metal to appreciable or detectable stretching, thereby avoiding thinning of the metal to any objectionable or detectable extent. In the final forming rolls, as in the preforming rolls, the metal strip is formed by being pulled about the forming elements or ribs and is at no time subjected to forming pressure between opposed pressure applying forming surfaces, particularly during relative movement thereof. In that manner, I further guard against tearing or rupture of the metal strip with the advantages above noted.

In some cases it is desirable to provide the corrugated metal strip with projections or bosses in the side walls of the corrugations, to increase air turbulence and metal contact. 1 preferably provide, for that purpose, a machine for preforming the metal strip and cutting it to desired length, and shape the preformed corrugated strip to final form by separate means. In Figure 14 I have shown a machine comprising a suitable frame 96 supporting a table 9'! on whichare mounted two uprights, one of which is shown at as, spaced apart transversely of the table. A lower preforming roll 99 is keyed on a shaft I09 rotatably mounted in the uprights 9t, and an upper preforming roll IUI is secured on a shaft rotatably mounted in flanged bearing blocks I92 seating in slots Hi3 extending from the upper ends of the respective uprights 98. The rolls 99 and IIII are similar to the preforming rolls 23 of Figures 1 and 2 and are geared together by spur gears in the same manner as the latter rolls and need not be further described. The lower roll 99 is driven by shaft 42 of a speed reduction unit (not shown) through bevel gearing, in the same manner as the lower roll 23 of Figure 1, but the bevel gearing is located at the same end of roll 99 as the spur gear on shaft I thereof for driving the upper roll IIH, it being understood that the two spur gears are at the far ends of the rolls 99 and IIII as viewed in Figure 14.

A spur gear IE4 is keyed on the near end of shaft I99, as viewed in Figure 14, of roll 99. This spur gear 104 meshes with a spur pinion I05 secured to the inner face of a cam disc I96, both rotatably mounted on a stub shaft I9'I secured in the upper end of a standard I98 suitably secured to table 9?. Disc Kit is provided with a radially projecting element or nose I69, disposed to contact a roller Ili) mounted in a slotted head III at the inner of a horizontal rod H2, slidably mounted through sleeves I I3 at the upper ends of posts IM, mounted on table 97 and spaced from standard I08 in the direction of travel of the metal strip through the machine. A compression spring I I5, disposed about rod H2 and confined between a collar IIB fixed thereon and the sleeve IIS more remote from standard I08, urges rod II2 toward the right so as to hold roller III? in contact with the cam disc I03. The rod H2 is provided at its outer end with a slotted head Ii'I connected by a link II8 to one arm of a two armed lever I20 rockably mounted at i2i in a bracket I22 secured to an upright I23 mounted on bed 97. As will be understood, there are two uprights I23 spaced apart transversely of bed 9? and connected at their upper ends by a cross plate I24. A block I25 is mounted on plate I2rl and carries a suitable knife I29 adjustable fore and aft thereon by known means. A knife holder I28 is slidably mounted between side guide members I29 extending upward from block I25. An upper knife I36 is mounted in the holder I23 and cooperates with the lower knife IZti for cutting to desired length metal strip passing therebetween. The lnife holder I28 is connected at its midlength, by a link I32, to the lower end of an arm I33 fixed on a cross shaft it i rockably mounted in bearing blocks I35 fixed on the upper ends of the side guides i293. An arm I31 is fixed on the near end of shaft I3 5, as viewed in Figure 14, and is pivoted at its to a clevis I39 at the upper end of a turn buckle I49. A clevis MI at the lower end of turn buckle I49 is pivoted at I42 to the upper arm M3 of the lever I29. The lower preforming roll 99 rotates counterclockwise, as viewed in Figure 14, the upper roll NH and the cam disc I06 rotating clockwise. When nose I99 of disc Hi6 contacts roller III the rod H2 is forced toward the left, thus pulling down the turn buckle I40 and thereby straightening the 9 toggle comprising link I32 and arm I33, thus moving the knife I36 downward into cooperating relation to the knife I26, for severing the metal strip therebetween, as will be understood from what has been said. The gear ratio is, of

course, such that the metal strip is cut to the 'desired length.

A roll I45 of metal strip or ribbon I lfi is rotatably mounted in the slotted upper ends of bracket arms I4! secured to andextending upwardly from the end of frame 96 adjacent rolls 99 and NH. Strip I45 is led from roll 455 between the rolls 99 and IOI and thence between :strip guides E48, mounted at the upper ends of posts I49 mounted on table 9-1, there being .two

.guides I48, as will be understood, receiving the transversely straight side marginal portions of .thepreformed corrugated strip. The guides M8 extend .from .the rolls 5.9 and IIlI to within a short distance of the licck I25, over which the .corrugatedstrip passes as it leaves the guides I48. The preformed corrugated strip leaving the rolls 99 and MI is similar to thestrip leavshaped to finalform between upper and lower .dies I50 and I I, respectively, which'are flat or straight lengthwise. The lower die I5I, which may be stationary, comprises a body portion I52 and a plurality of substantially parallel ribs I53 projecting upwardly therefromand of undulatory formation lengthwise, that is, transversely of body I52, for the major portion of their length, being provided with terminal elements I541 which are straight transversely of body I52. The ribs I53 'are'generally similar to the ribs 42* of the final forming rolls 24 of Figures 1 and 2, have flat upper edges, are provided with upwardly extending bosses or projections I55 of substantially semi-elliptical shape at the outer sides of their undulations, have an effective height, not including the bosses I55, less than the ribs of'the rollers 99 and I III by the height of the bosses I55, and are spaced apart a distance somewhat greater than thedistance between the ribs of the rollers 99 and IIJI, in thesame manner as the 'ribs 42 of the final forming rolls 24 of 'F'igures 1 "and 2 are spaced relative to the ribsZ'B o'f'the preforn'iing rolls "23.

The ribs I53 01 die I5I are further provided,

at the outer sides of the undulations'thereof, with'bosses or projections I56 of substantially rectangular shape in plan, merging smoothly at their sides into the undulations of the ribs 153 and having rounded corners, the faces of the bosses I55 away from the undulations of the ribs I53 being fiat and substantially perpendicular tobody I52 'of the die I5I. 'The'topsor upper faces of the'bosses I56 are nearly flush'with the upper edges of the ribs I53.

A-cover plate 158, provided with an upwardly off-set flange 159, is secured-to the under face of die I5I, conveniently by screws I60, there being a sealing gasket I'5I between 'fiange I59 and the under face of die I 5|. Plate-I58 defines, with die I 5!, an air chamber "I62 "from -which restricted passages or ducts I63 extend upwardly through body I52 and open into the spaces between the ribs I53, "one of such ducts being shown and it being understood that any suitable numberthereof appropriately disposed may be .provided. Air under appropriate pressure may be admitted to the chamber I62 through a hose I64 secured to a nipple I65 opening through plate I58 and secured thereto in a suitable manner, conveniently'by welding. By admitting air under pressure to the chamber I52 the finally formed strip in the die I5I may readily be raised and removed therefrom, as will be clear from what has been said.

The upper die I50 maybe moved toward and away from .the lower die I.5'I in any suitable known manner. .Itis similar to the die I5I with the exception that it is not provided with the cover plate 58 and the ducts I63. Upper die I 50 .is provided with ribs I68 the sameas the ribs IE3 of lower die I 5|. The ribs I68 are spaced apar the same distanceas .the ribs I53 of lower die IM and the ribs of each of the two dies I50 and MI are oiT-setrelative to the ribsof the other die one-half the distance between two adjacent ribs so that, when the dies are closed, the ribs of each thereof extend midway between the ribs of the other die withsubstantial clearance therebetween, materially greater than the thickness of the metal strip.

Referring further to Figures 16 and 17, I'have shown in Figure 16 two of the ribs I68 of the upper die 553, in dot-and-dash lines, in-the position which they occupy between adjacent ribs I53 of the lower die I5I, when the diesare closed. It will be noted .that .the laterally projecting bosses I68 at the outer sides of the undulations of the ribs I68 .are aligned with the inner or concaved sides of the undulations of the ribs I53 of the lower die, with clearance I'm therebetween materially greater than the thickness of the metal strip. In the final forming operation the preformed metal strip Mfiais placed in the lower die I5I and .the dies are then .closed by downcorrugations of the preformed metalstrip are pulled or bent around the bosses I56 and IE9 of the ribs I53 and IE8, respectively, of the lower and upper dies I5I and 15!], so as to be shaped thereabout. The bosses I55 of ribs-I53 bend upward corresponding areas of the crest of the upwardly extending corrugations of thepreformed metal strip, and bosses I12 of ribs f I 68 bend downward corresponding areas of the crests of the downwardly extending corrugations of the preformed metal strip M611. Referring further to Figure 17, when the dies I5I!.and I5! are closed, the bosses I56 of ribs I53 of the .lower die I5I are disposed in alignment with the inner or concaved sides of the undulations of ribs I63 of the upper die,'with clearance I'II] therebetween materially greater than the thickness of the metal strip.

It will be seen that, during the final forming operation, the metal strip is shaped about the ribs and the bosses thereof by pulling'or bending of the metal thereabout, and Without at' any time subjecting the metalof the strip to'forming pressure between opposed pressure applying relatively moving forming surfaces. That avoids rupture or tearing of the metal strip with the advantages above noted. Further, since the preforming elements or ribs are of greater effective height than the final forming elements or ribs, adequate metal is available for shaping the preformed strip to desired final form, the final forming operation being mainlya simple bending operation in which the walls of the corrugations of themetal strip are defiectedand shaped'about the bosses of the ribs without appreciable stretching of the metal. In that manner, objectionable thinning of the metal is avoided.

The finally formed metal strip produced by the dies of Figures to 17, inclusive, is shown in Figures 18 and 19. This finally formed metal strip is provided with corrugations H5 extending transversely of strip M52) and of undulatory formation lengthwise for the major portion of their length, the corrugations H5 having terminal element H6 straight transversely of strip Sic. Bosses ll! of approximately semi-elliptical shap in plan project from the crest of the ribs or corrugations H5, at the outer sides of the undulations thereof, and bosses W8 project laterally from the outer or convexed sides of the undulations of the corrugations. The bosses H8 are of substantially triangular shape in vertical section, as shown in Figure 19, and those of each corrugation extend oppositely to those of the next adjacent corrugation, it being noted that the base of the respective bosses [i8 is substantially flush with the crest of the associated rib or corrugation H75.

If desired, instead of reforming the preformed metal strip produced by the machine of Figure 14 between the fiat dies I and E of Figures 15 and 16, to form the bosses H8 on the corrugations N5, the reformed strip produced by the machine of Figures 1 and 2 may be subjected to a further reforming operation between the dies (59 and I51. If that procedure is followed, which may be desirable in certain cases as simplifying the die forming operation, the metal strip is subjected to a preforming operation and then to two successive reforming operations, as will be clear from what has been said. In either case, the height of the corrugations produced in the preforming operation is such as to assure that the metal rendered available by reduction in height of the corrugations in th first or succeeding reforming operation is adequate for performance of that operation without stretching of the metal. When the corrugated metal strip is reformed in the dies I50 and IE], to form the bosses 578, the operation is to a considerable extent a simple bending operation, though some stretching of the metal, but not to an objectionable extent such as to risk rupture thereof, oc-

ours.

The finally formed lengths of metal strip are used in constructing cores of heat exchangers, such as automobile heaters and radiators. In my copending application, Serial No. 142,796,

filed February '7, 1950, I have disclosed a cellular core for heat exchangers, in which metal strip formed as herein disclosed is used to advantage to provide the cooling air passages. Opposed lengths of metal strip, corrugated as shown in Figure 13 of the instant application, are positioned between water wall strips defining between them water passages, the latter strips having transverse ribs upon which the corrugation of the air passage strips seat, being positioned thereon by the bosses 9?; of Figure 13. The opposed corrugated air passage strips define between them undulatory air passages which impart high turbulence to air flowing therethrough, as Well as large area of contact between the air and the metal, thereby attaining high efiiciency in heat transfer. I have found that by providing the corrugated metal strip for the air passages with laterally projecting bosses, such as the bosses lit of Figures 18 and 19 of the instant application, the efiiciency of the core can be materially increased, due to resultant increase in air turbulence and in area of contact of the air with the metal.

It will be understood that changes in detail may be made, both as to the apparatus and the method of my instant invention, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred forms only of my invention have been disclosed.

I claim:

1. In a machine for corrugating metal strip of predetermined thickness, 2. pair of spaced parallel preforming rolls and a pair of spaced parallel final forming rolls parallel with and disposed to receive preformed metal strip from said preforming rolls, the rolls of each pair respectively having a plurality of substantially uniform thickness and uniformly spaced lengthwise ribs of undulatory formation lengthwise and being relatively off-set angularly approximately one half the distance between adjacent ribs of the respective rolls, the spacing and effective height of the ribs of the rolls of each pair of being such that in the rotation thereof the ribs of each roll enter substantially midway between the ribs of the other roll to approximately the final depth of the desired corrugations with clearance therebetween materially greater than the thickness of the metal strip, the height of the ribs of the preforming rolls being greater than the height of the ribs of the final forming rolls to provide metal for final forming of the strip without objectionable stretching 0 thereof, and means for rotating the rolls of each pair at the same speed and in opposite relation while rotating the corresponding rolls of said pairs at the same speed and in the same relation.

2. The method of corrugating metal strip which comprises, preforming the strip in a single operation to provide in the strip transverse corrugations of undulatory formation lengthwise and V-shape in cross section by bending the strip over and between spaced preforming elements and without subjecting the strip to forming pressure between opposed relatively moving forming surfaces, and bending the corrugations of the resultant preformed strip over and between spaced final forming elements similar to said preforming elements and substantially paralleling said corrugations and thereby forming the crests of the latter to desired final shape and size without subjecting the corrugations to forming pressure between opposed relatively moving forming surfaces while maintaining the continuity of the corrugations of the preformed strip and the V cross section of the corrugations produced in the preforming operation.

3. The method of corrugating metal strip which comprises, preforming the strip in a single operation by pulling and bending it in alternately opposite directions over and between rounded spaced preforming elements of undulatory formation lengthwise, thereby producing in the strip corrugations of undulatory formation lengthwise and V shape in cross section and of a height approximating the desired final height thereof without sub- J'ecting the strip to forming pressure between opposed relatively moving forming surfaces, and bending the corrugations of the resultant preformed strip between final forming elements similar to said preforming elements and spaced apart a distance approximately the same as the distance between the crests of ad acent preformed corrugations of the strip and thereby shaping the crests of the corrugations of the preformed strip to desired "finalform and height without subjecting the pre- "formedstrip to forming pressure between opposed relatively moving forming surfaces while maintaining the V' :cross section of the corrugations produced in the preforming operation.

4. The method of corrugating metal strip which comprises, preforming the strip in a single operation by pulling and bending it in alternately oppositedirections over and between spaced Preforming elements of undulatory "formation -lengthwise, thereby producing in the strip corruing surfaces, and bending the-corrugations of'the resultant preformed strip between flat forming elements similarto said preforming elements and :spaced aadistanoeapartapproximately the same as the distance between the crests of adjacent preformed corrugations and thereby flattening the crests of the corrugations without otherwise materially altering the shape or height thereof and without subjecting the preformed strip to forming pressure between opposed relatively moving forming surfaces.

5. In a machine for corrugating metal strip of predetermined thickness, a pair of spaced parallel preforming rolls having a plurality of uniformly spaced ribs of substantially uniform thickness and of undulatory formation lengthwise and having rounded radially outer edges, said rolls being relatively off-set angularly approximately on half the distance between adjacent ribs of the respective rolls, the spacing and effective height of the ribs of each roll being such that in the rotation thereof the ribs of each roll enter substantially midway between the ribs of the other roll to a depth approximately the same as the final depth of the desired corrugations with clearance between said ribs such that corrugations of V-shape in cross section will be formed in metal strip passed between said rolls without subjecting the metal strip to forming pressure between opposed forming surfaces, a pair of spaced final forming rolls parallel with said preforming rolls and disposed to receive from the latter preformed metal strip, said final forming rolls having a plurality of uniformly spaced ribs of substantially uniform thickness and of undulatory formation lengthwise and having fiat radially outer edges, said final forming rolls being relatively off-set angularly approximately one half the distance between adjacent ribs of the respective final forming rolls, the spacing and effective height of the ribs of each final forming roll being such that in the rotation thereof the ribs of each final forming roll enter substantially midway between the ribs of the other final forming roll to a depth the same as the final depth of the desired corrugations and contact the corrugations of the preformed metal strip at the crests only of the corrugations thereof thereby flattening such crests without subjecting the metal strip to forming pressure between opposed forming surfaces while maintaining the cross sectional V-shape of the corrugations formed by said preforming rolls, and means for rotating the rolls of each pair at the same speed and in opposite relation while rotating the corresponding rolls of said pairs at the same speed and in the same relation.

6. In means for corrugating metal strip of predetermined thickness, a pair of opposed preforming members each having a body portion and spaced substantially parallel ribs projecting therefrom toward the othermember and of undulatory formation lengthwise, said members being relatively off-set approximately one half the distance between adjacent ribs of the respective ,members, said ribs being so spaced and of such efiectiveheight that the ribs of each member will enter substantially midway between theribs of the other member with.clearance'therebetween such that corrugations of V-shape in cross section will beformed in metal strip passed between said members in the relative cooperating movement thereof without subjecting the metal strip to forming pressure between opposed forming sur- .faces, and a pair of opposed final forming members each having a body portion and substantially parallel ribs similar to and of approximately the same spacing and-effective height as the ribsof said preforming members wherebysaid ribs of .said final forming members contact the crests only of the corrugations of the preformed metal strip and form the crests to desired final shape without otherwise altering the shape of the corrugations produced by said preforming members and without subjecting the metal strip to forming pressure between opposed forming surfaces.

'7. In means for corrugating metal strip of predetermined thickness, a pair of spaced preforming rolls each comprising a body and a plurality of lengthwise ribs thereon projecting outward therebeyond and uniformly spaced circumferentially of said roll, said ribs being of undulatory formation lengthwise, and of such effective height and spacing that in the rotation of said rolls the ribs of each roll enter substantially midway between the ribs of the other roll and in cooperation therewith form in metal strip passed between said rolls corrugations of V-shape in cross section and of undulatory formation lengthwise without subjecting the metal strip to forming pressure between opposed forming surfaces, a pair of opposed final forming rolls parallel with said preforming rolls disposed to receive from the latter preformed metal strip, said final forming rolls having ribs similar to and of approximately the same effective height and spacing as the ribs of said preforming rolls whereby the ribs of said final forming rolls contact the crests only of the corrugations of the preformed metal strip and form the crests to desired final shape without otherwise altering the shape of the corrugations produced by said preforming rolls and Without subjecting the metal strip to forming pressure between opposed forming surfaces, and means for rotating the rolls of each pair at the same speed and in opposite relation while rotating the corresponding rolls of said pairs at the same speed and in the same relation.

8. The method of corrugating metal strip which comprises, preforming the strip by bending it in alternately opposite directions over and between preforming elements of undulatory formation lengthwise and of uniform thickness,

thereby producing in the strip corrugations of undulatory formation lengthwise and V-shape in cross section and of approximately the desired final height without subjecting the strip to form ing pressure between opposed relatively moving forming surfaces, disposing the corrugations of the preformed strip over and between final forming elements similar to said preforming elements and of uniform thickness the same as the desired final width of the crests of the corrugations with said final forming elements contacting the cor- 15 rugations at the crest areas only thereof, and flattening the crests of the corrugations by pressure applied thereto solely by said final forming elements while retaining substantially unaltered the V cross section of the corrugations imparted thereto in the preforming operation.

9. The method of corrugating metal strip which comprises, moving the strip in one direction and during such movement bending it in alternately opposite directions over and between preforming elements of undulatory formation lengthwise having rounded working edges and of uniform thickness approximately the same as the desired final width of the crests of the corrugations, thereby producing in the strip corrugations of undulatory formation lengthwise having rounded crests and V' shape in cross sec tion and of approximately the desired final height without subjecting the strip to forming pressure between opposed relatively moving forming surfaces, during continued travel of the strip in said one direction disposing the corrugations of the preformed strip over and between final forming elements having fiat working edges and similar to said preforming elements and of uniform thickness the same as the desired final width of the crests of the corrugations with said final forming elements contacting the corrugations at the crest areas only thereof, and during such continued travel of the strip flattening the crests of the corrugations by pressure applied thereto solely by said final forming elements while retaining substantially unaltered the V cross section of the corrugations imparted thereto in the preforming operation.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,018,399 Livingston Feb. 20, 1912 1,365,258 Lundin Jan. 11, 1921 2,258,443 Bruker Oct. 7, 1941 2,290,608 Evans July 21, 1942 2,406,051 Weiss Aug. 20, 1946 

